This application may be related to Applicant"" concurrently filed application Attorney Docket No. PET 1883, entitled xe2x80x9cProcess For Producing, Jointly Or Otherwise, Monoalkyl Aromatic Compounds, Dialkyl Aromatic Compounds And Trialkyl Aromatic Compoundsxe2x80x9d, based on French Application 00/05.677 filed May 2, 2000.
1. Field of the Invention
The process that is the object of this application is a process for alkylating or transalkylating aromatic compounds for the purpose of producing alkylaromatic compounds. The aromatic monoalkyls find a use in the composition of gasolines or lyes, aromatic dialkyls and trialkyls in the field of lubricants.
The process according to the invention thus makes possible the production of mono-, di- and trialkyl aromatic compounds. This process thus relates to the alkylation of aromatic compounds (benzene, toluene, cumene) by alkylating agents (olefins, alcohol, halides) for producing aromatic monoalkyls whose grafted aliphatic chain comprises a carbon number that is selected from 2 to 20 carbon atoms.
2. Background of the Invention
This process can also produce dialkylbenzenes, i.e., aromatic compounds where the benzene core comprises two paraffin chains whose carbon atom number can be identical or different. Each of these aliphatic chains can contain 2 to 20 carbon atoms. In the case where it would be desired to produce aromatic trialkyls, there are three aliphatic chains of which two, for example, have identical lengths.
The alkylation of aromatic compounds has been known for many years.
U.S. Pat. No. 2,939,890 (Universal Oil Products Company), dating from 1960, thus claims a process for synthesis of cumene by using BF3 as a catalyst.
U.S. Pat. No. 3,173,965 (Esso Research), dating from 1965, which claims as suitable catalysts for the alkylation of benzene acids of type AlCl3, AlBr3, FeCl3, SnCl4, BF3, H2SO4, P2O5 and H3PO4, is also known.
In the same connection, U.S. Pat. No. 4,148,834 (1979) and U.S. Pat. No. 4,551,573 (1985) claim the use for the first of HF during the first stage and AlCl3 or AlBr3 in the second stage. The second patent claims, more particularly, a mixture of aluminum halides and elementary iodine.
U.S. Pat. No. 3,251,897 claims the use of X and Y zeolites that are exchanged with rare earths for the production of monoalkyl benzene (ethylbenzene, cumene) and diethylbenzene. 
The dialkylbenzenes are compounds whose characteristics one extensively described.
American U.S. Pat. No. 3,173,965 describes the properties of products of general formula (I) whose R1 and R2 alkyl chains are located in para-position on the benzene cycle. These chains have between 4 and 15 carbon atoms for R1 and between 10 and 21 carbon atoms for R2. The patentees emphasize in particular that the dialkylaromatic compounds whose alkyl groups are in ortho and meta position have the least advantageous lubricating properties.
U.S. Pat. No. 3,478,113 teaches the properties of a synthetic oil of the same general formula 1. In this case, R1 has between 6 and 15 carbon atoms and R2 has between 14 and 24 carbon atoms. The sum of the aliphatic carbon number should be between 20 and 30 carbon atoms. The product can be substituted in the ortho or in the para. The generic formula specifies that the carbons in alpha position of the phenyl group are secondary carbons for the R1 and R2 groups (Rxe2x80x94CH2xe2x80x94Phxe2x80x94CH2xe2x80x94Rxe2x80x2 with R1=Rxe2x80x94CH2 and R2=Rxe2x80x2xe2x80x94CH2).
European Patent EP 168534 describes the properties of synthetic oils of the same generic formula I. In this case, R1 has between 2 and 4 carbon atoms and R2 has between 14 and 18 carbon atoms. These oils have overall between 23 and 28 carbon atoms that correspond to between 17 and 22 aliphatic carbon atoms. The patentees reveal good physical properties of these oils when one of the two alkyl chains is much shorter than the other.
U.S. Pat. No. 4,148,834 teaches a process that makes it possible to improve the physical properties of the oils by synthesizing the latter in two successive stages:
synthesis of monoalkylbenzene by using hydrofluoric acid HF as a catalyst,
obtaining dialkylbenzene starting from monoalkylbenzene that is obtained during the first stage by using aluminum chloride or bromide as a catalyst.
In the final product, R1 and R2 comprise between 6 and 18 carbon atoms. The product is characterized by the presence of the phenyl group on carbon 2 of the aliphatic chain with a rate that is greater than 20% in one of groups R1 or R2 and less than 20% in the other.
This invention relates to a synthetic oil that comprises wholly or partly of dialkylbenzenes and/or partially or totally hydrogenated dialkylbenzenes. The synthetic oil according to the invention can also be used as an oil base or oil base additive and comprises at least one dialkylbenzene and/or at least one partially or totally hydrogenated dialkylbenzene and meets a general chemical formula:
R1xe2x80x94Axe2x80x94R2. 
in which R1 and R2 represent alkyl groups and A is a benzene core and/or a cyclohexane core and/or a cyclohexene core and/or a cyclohexadiene core and is characterized in that it contains between 1 and 20% by weight of ortho isomers and in that at least one of the alkyl groups is attached for the most part to group A by carbon 2 of the aliphatic chain. The two alkyl groups are preferably attached for the most part to group A by carbon 2 of the aliphatic chain. Within the meaning of this description, the term for the most part means that at least 50% of at least one of the alkyl groups is attached to group A by carbon 2 of the aliphatic chain and usually at least 80%, often at least 95%, and most often virtually 100%.
The oils according to this invention have viscosity numbers that are much higher than those that it has been possible to describe in the prior art as well as very low pour points.
Another characteristic of the synthesized oils, conditioned by the mixture of hydrocarbons used, resides in very low values for these compositions of the Noack volatility, much less than those obtained with the best lubricating oils described in the prior art. As has already been emphasized, this characteristic is very important because it affects the service life of the lubricating base. A strong Noack volatility is also reflected by a significant atmospheric pollution, a short service life of the oil and the obligation of a frequent renewal, and it therefore poses in particular the economical and ecological problem of storage and treatment of waste oils.
It was found, surprisingly, that the physical properties of the oils described by formula I depend on the proportions of the ortho compound. High viscosity numbers and very low Noack volatilities were found when the synthesized oil according to the invention comprised partially or totally hydrogenated dialkylbenzenes in proportions of between 1 and 20% by weight of ortho isomers and preferably between 3 and 15% by weight. The oil preferably comprises a benzene core and/or a cyclohexane core and/or a cyclohexene core and/or a cyclohexadiene core that has two substituents that consist of aliphatic chains in meta position in proportions of between 1 and 50% and preferably between 3 and 50% by weight. The oil preferably comprises a benzene core and/or a cyclohexane core and/or a cyclohexene core and/or a cyclohexadiene core that has 2 substitutents that consist of aliphatic chains in para position in proportions of between 10 and 95% and even more preferably between 40 and 95% by weight. The sum of the isomers that are present and contained in the oil is equal to 100%. The three isomers are preferably present in the synthetic oil.
The compositions of synthetic oils according to this invention can be obtained by adjusting the proportion of isomers by a simple addition of ortho isomers and/or meta isomers and/or para isomers or equally by all of the synthesis techniques that are known to one skilled in the art.
The dialkylbenzenes can be, for example, prepared by alkylation of benzene with olefins. For this reaction, benzene and pure alpha-olefins whose chain length varies between 6 and 20 carbon atoms and preferably between 8 and 20 atoms were used.
These olefins are mixed with benzene in a molar ratio of benzene to olefin of about 0.1:1 to about 10:1. Preferably, a ratio of between 0.2:1 and 6:1 will be used, and even more preferably between 0.5:1 and 3:1.
Two main types of dialkylbenzenes were prepared:
A type called symmetrical DAB in this description for which the two alkyl chains have the same number of carbon atoms,
a type called asymmetrical DAB in this description for which the two alkyl chains have a different number of carbon atoms.